This invention relates to a heat-sensitive transfer recording medium, more particularly to a heat-sensitive transfer recording medium capable of printing letters at low energy with high transfer sensitivity and also capable of suppressing generation of ground staining (fog) on the recording sheet such as plain paper.
Heat-sensitive recording medium has heretofore been employed as the recording medium for forming an image on a recording sheet such as plain paper by transfer by means of a thermal printer or a thermal facscimile, etc. Such a heat-sensitive recording medium has at least one colorant-containing layer provided on a support, and a typical colorant-containing layer known in the art comprises a coloring agent made of a dyestuff such as a pigment, etc. and a heat-fusible material. For such a heat-fusible material, low melting materials such as waxes, etc. have been employed. On the other hand, for the support, in order to obtain good reproducibility of the dyestuff transferred image obtained from the colorant-containing layer coated thereon, films excellent in surface smoothness and dimensional stability have been employed.
For recording a dyestuff (or dye) transferred image on plain paper, etc. by use of such a heat-sensitive transfer recording medium, it is desired to print letters at low energy when utilizing a thermal printer or a thermal facscimile having a thermal head. However, the heat-sensitive transfer recording medium of the prior art had insufficiently low transfer sensitivity. Also, there was also involved the drawback of generation of ground staining (fog) on the recording sheet.
As one method for enhancing transfer sensitivity, there is disclosed the technique of improving thermal conductivity of the colorant-containing layer in Japanese Provisional Patent Publication (KOKAI) No. 75894/1981. The invention disclosed in this Patent Publication is a technique incorporating a powdery thermoconductive material in a colorant-containing layer, which requires use of an additive, and therefore the colorant-containing layer becomes thicker depending on the additive employed, whereby resolution of the image may sometimes be lowered. Also, there was involved the drawback of generation of ground staining (fog) on the recording sheet.